Field of the Invention
The manufacturing of ring-type joints started with high pressure and high temperatures applications mainly for the oil industry in the drilling field and other termination equipments. Currently, they are also used in valve devices as well as pipes for high pressure containers requiring good integration.
Said joints are well known in the oil industry both in the production as well as in the refining stages. They are manufactured under the following standard: API specification 6A and ASME specification B16.20.
These joints are used in high pressure lines, both for high and low temperature, including sour gas and corrosive atmospheres. The surface finishing and the hardness are important factors for this type of joints which have to be softer than the flange material that is to contain them, in order to ensure an effective seal.
Different techniques are known to manufacture metal joints for high pressure ducts, for example, DAN-LOC and LAMDN'S joints in the USA and Francis B Will Mott LTD and FLEXITALLIC LTD in England.
Practically, all conventional design of ring-type joints have the same oval shape, FIG. 4, and particularly, octagonal shape. When starting from a round bar, said bar is machined into an oval shape, FIG. 3, and if a square or rectangular bar is used, it is machined as well. In general, in all the cases, the same basic procedure is used, but the difference is the use of rectangular or square bar, FIG. 3, depending on the market availability, since the annual volume sales for some models, does not justify special manufacturing at the mill.
The disadvantages of the abovementioned process is that because it starts from a rectangular or square bar, FIG. 3, there is a lot of waste in the form of burr, the machining times are longer and there is a higher wear of the machine tools.